Heart function in morbidly obese patients returns to normal after bariatric surgery but not after lifestyle intervention, according to research ‘Effect of weight loss on subclinical myocardial injury: A clinical trial comparing gastric bypass surgery and intensive lifestyle intervention ‘, published in the European Journal of Preventive Cardiology. The results suggest that bariatric surgery may reduce the risk of cardiovascular disease in morbidly obese patients. Approximately one in five western Europeans is obese, while around 2 to 3% are morbidly obese.

"This is one of the first studies showing that an intervention can reduce mildly elevated cardiac troponin levels," said author Professor Torbjørn Omland, professor of medicine at the University of Oslo. "High-sensitivity troponin I is a good marker of how much stress the heart is exposed to. Marked weight loss induced by bariatric surgery seems to have a direct effect on the health of the heart and reduces strain to normal levels."

The study published investigated whether weight loss by bariatric surgery could reduce levels of high-sensitivity cardiac troponin I (hs-TnI) in morbidly obese patients, which would indicate reduced cardiac stress and chronic subclinical cardiac injury. Cardiac troponins are traditionally used to diagnose acute ischaemic injury and confirm that a patient had a heart attack. The more recent high-sensitive test also identifies low-grade, chronic cardiac damage in patients who do not have established cardiovascular disease.

Concentrations of hs-TnI were compared between 74 morbidly obese patients who had Roux-en-Y gastric bypass, 62 morbidly obese patients who exercised and restricted their calorie intake, and a control group of 30 people with normal weight.

"The extensive weight loss that we saw with the surgery group was associated with a drastic reduction in hs-TnI levels," said lead author Dr Magnus N Lyngbakken, a PhD candidate at the University of Oslo in Norway. "The group that exercised and ate less showed no such significant reduction in levels of hs-TnI. Twelve months after surgery levels of hs-TnI were the same in the surgery group as in the control group of normal weight. It's too early to tell, but if this translates into less heart failure, heart attacks and cardiovascular deaths, then this could mean that morbidly obese patients who have bariatric surgery obtain a cardiovascular risk comparable to a normal weight population."

At the beginning of the study, hs-TnI levels were 2.40ng/L in the bariatric surgery group, 2.35ng/L in the lifestyle intervention group, and 0.90ng/L in the normal weight group. At 12 months after the intervention, hs-TnI levels decreased significantly in the surgery group (p<0.001) but not in the lifestyle group (p=0.087). The surgery group lost 30% of their body weight on average while the lifestyle intervention group lost an average of 8% (p<0.001).

"Bariatric surgery reduces the stress on the heart through a reduction in body weight. It also improves the cardiometabolic milieu of the body, as reflected by the drop in triglycerides, which has beneficial effects on heart muscle cells,” added Omland. "Our findings and those of other studies all point to bariatric surgery being superior to lifestyle intervention with regard to the beneficial effects on the heart. Much of that can be explained by the greater weight loss induced by bariatric surgery. Although lifestyle intervention leads to a transient reduction in weight, its impact in the long term is not as great as surgery."

Interestingly, after 12 months hs-TnI levels in the surgery group were not significantly different from the normal weight group (1.30 vs 0.90ng/L, p=0.54). In the lifestyle intervention group, however, hs-TnI levels remained significantly higher than in the control group (2.15 vs 0.90ng/L, p=0.003). Subsequent analysis showed that changes in body weight and serum triglycerides may mediate the change in hs-TnI achieved with surgery.

“In patients with morbid obesity, bariatric surgery was associated with a significantly greater reduction in high-sensitivity cardiac troponin I, an index of subclinical myocardial injury, than intensive lifestyle intervention,” the study authors concluded. “The reduction appeared to be mediated by reductions in body weight and serum triglycerides. This suggests that weight loss following bariatric surgery may reduce cardiometabolic stress and subsequent risk of heart failure.”

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